1. Technical Field
The present invention pertains to improvements in methods and apparatus for surgical drapes utilized in thermally treating surgical sterile fluid media. In particular, the invention is an improvement of the methods and apparatus disclosed in U.S. Pat. Nos. 4,393,659 (Keyes et al), 4,934,152 (Templeton) and copending U.S. patent application Ser. No. 08/399,975. The disclosures in those patents are expressly incorporated by reference herein in their entireties.
2. Discussion of the Prior Art
The Keyes et al patent discloses a surgical slush producing system having a cabinet with a heat transfer basin at its top surface. A refrigeration mechanism in the cabinet takes the form of a closed refrigeration loop including: an evaporator in heat exchange relation to the exterior of the heat transfer basin; a compressor; a condenser; and a refrigeration expansion control, all located within the cabinet. A separate product basin is configured to be removably received in the heat transfer basin. Spacers, in the form of short cylindrical stubs or buttons are arranged in three groups spaced about the heat transfer basin and projecting into the heat transfer basin interior to maintain a prescribed space between the two basins. During use, that space contains a thermal transfer liquid, such as alcohol or glycol, serving as a thermal transfer medium between the two basins. A sterile sheet of material, impervious to the thermal transfer medium, is disposed between the product basin exterior and the liquid thermal transfer medium to preserve the sterile nature of the product basin. Surgically sterile liquid, such as sodium chloride solution, is placed in the product basin and congeals on the side of that basin when the refrigeration unit is activated. A scraping tool is utilized to remove congealed sterile material from the product basin side to thereby form a slush of desired consistency in the product basin.
As noted in the Templeton patent, the above-described system has a number of disadvantages. In particular, a separate product basin must be removed and resterilized after each use. Additionally, the glycol or other thermal transfer medium is typically highly flammable or toxic and, in any event, complicates the procedure. The Templeton patent discloses a solution to these problems by constructing an entirely new apparatus whereby the product basin is eliminated in favor of the sterilized drape impervious to the sterile surgical liquid, the drape being made to conform to the basin and directly receive the sterile liquid. Congealed liquid is scraped off the sides of the conformed drape receptacle to form the desired slush.
In addition, Templeton also provides an electrical heater disposed at the bottom of the basin to convert the sterile slush to warmed liquid, or to heat additional sterile liquid added to the basin. Templeton describes the need for such warmed sterile liquid as occurring after a surgical procedure is completed to facilitate raising the body cavity of the surgery patient back to its normal temperature by contact with the warm liquid.
The present invention is an improvement in the drape disclosed in copending U.S. patent application Ser. No. 08/399,975. The thermal treatment system disclosed in that application includes a plurality of basins adjacent each other for producing sterile slush and heating a sterile liquid respectively. A surgical drape is sufficiently large to be placed over the thermal treatment system and is pushed down into the basins to form drape receptacles for containing the sterile liquid. The drape includes centering indicia for indicating the centers of the basins wherein surrounding portions of the drape adjacent the centering indicia are pushed into the basins until the centering indicia reside at the approximate center of the lowermost portion or bottom of the basin in order to form the drape receptacles. However, the drape including centering indicia lacks the desired capability of directing proper initial placement of the drape on the thermal treatment system. In particular, the centering indicia do not indicate the proper orientation or alignment of the drape on the top surface of the thermal treatment system and therefore the drape may not uniformly cover the thermal treatment system, thereby risking possible contamination of the sterile liquid. The centering indicia also do not indicate the proper direction and sequence in which to unfold the drape once the drape is removed from a package, thereby often requiring the drape to be refolded and realigned. Further, the centering indicia do not provide guidance as to the proper length of the drape overhanging the top surface of the thermal treatment system and therefore may increase the risk of contamination to the sterile liquid due to improper placement of the drape.